Temen-ni-gru

The Temen-ni-gru is an unholy tower constructed by devil worshippers. Originally sealed by The Dark Knight Sparda deep underground, Arkham and Vergil have resurrected it in the present day.

Before Devil May Cry 3
It was sealed two thousand years in a complex ritual requiring Sparda to confiscate the names of fallen angels representing the seven deadly sins, imprison the tower's 7 gatekeepers, and seal away Leviathan as well as his own demonic power. Sparda, in the depths of the tower, let flow his own blood and that of a pure priestess, sealing the tower and his own accursed power. As an added level of security, Sparda also created the Perfect Amulet and split it in two such that both halves would be needed to awaken the Sword of Sparda.

Devil May Cry 3
Arkham explains to Vergil that resurrecting the tower is the way to obtain his father's ultimate power, so they begin to undo the seals Sparda placed on the tower. Vergil first renames the fallen angels, and then sends Arkham, along with some demons, to persuade Dante to come to the tower so that he can complete the Amulet. Soon after, they raise the tower and begin the rituals to awaken it. Arkham's daughter, Lady, is also enticed to enter the tower, but Arkham keeps her importance as a descendant of the priestess a secret from Vergil, who works on undoing Sparda's spell in the "Lair of Judgment", a sacrificial chamber at the bottom of the tower. Meanwhile, the mysterious demon Jester leads Dante to Vergil, with Dante slaying all the gatekeepers in his way.

Vergil places the completed Amulet in the control panel and begins bloodletting himself, but is unsuccessful in undoing the final seal. When Dante intrudes upon him, he attacks Dante in the hope that more of "Sparda's blood" will solve the problem, but nothing happens until Lady joins the fight and Arkham arrives. He reveals his identity as Jester, and that the final key to the seal is Lady's blood. After undoing the seal, he stalls the three fighters, taunting them for falling right into his trap, until the Tower activates and they fall off the central platform. As the platform rises through the tower, collecting huge, demonic bells representing the seven sins, the others race to the top to stop Arkham. However, he reaches the peak of the tower and calls upon the sins in a chant which unseals the final door to the Demon World. As the demonic bells ring and Blood-goyles flock around him, Arkham rises into the Demon World and takes the Force Edge, assuming Sparda's form and power. Although the portal to the Demon World has been shut closed it is unknown what happens to the Temen-ni-gru after Devil May Cry 3 as it is last place seen where Dante returns Lady's bazooka.

First Floor

 * Ice Guardian's Chamber - the only way to the main Temen-ni-gru, a room covered in thick ice, which became enterable from 13th Avenue. Here Cerberus the Ice Guardian is chained, protecting the entrance to Chamber of Echoes. Dante killed Cerberus here and acquired his namesake weapon, but not before Cerberus sealed the exit with a wall of ice. Dante also met Lady here for the first time, who entered by breaking through the upper part of the wall on her bike. Her rocket, shot in Dante's direction, made a hole in the ceiling, which was used by her to proceed
 * Chamber of Echoes (first floor) - a tall, open hall that is accessed from Ice Guardian's Chamber. It has a skeletal angel statue in the bottom and three stages of partially broken spiral roundwalks. The Vajura is located on a third stage, but the way to it and to the upper part is blocked by the walls. They slide into the main wall when Astronomical Board is placed on the second floor. This also activates a Jump Pad in the bottom. There are also a blue door and a red one, that lead to western and eastern Entranceway respectively, but the later is blocked by wall of fire, that can be extinguished by Siren's Shriek. An elevator shaft is also here, but the elevator can only be brought from Lift Room.
 * Entryway (west) - a corridor that connects Chamber of Echoes and Cursed Scull Chamber. There as a dead end that seems to be used as a small storage.
 * Cursed Skull Chamber - a room, accessed through western Entryway, which at first look resembles a dead end where a wall with skulls blocks the way immediately. It, however, can be easily smashed to reveal a small room with a switch that lowers a cage with skulls. If it is destroyed before it returns to the top, a Crystal Skull can be received from it.
 * Entryway (east) - a corridor that connects Chamber of Echoes and Living Statue Room.
 * Living Statue Room - a room with many Enigma-like statues, some of which are dormant and some are actually Enigmas. It is accessed through eastern Entryway and leads to Silence Statuary. Here the Vajura can be placed in a mechanism to open a cage with the Soul of Steel inside.
 * Silence Statuary - a room, accessed from Living Statue room, with many non-animated chessmen. Some of them block the elevator, that is activated by switch nearby leads to Incandescent Space, and need to be destroyed in order to proceed.
 * Chamber of Sins - a dark sewer-like room with piles of bones without any normal means of entry or exit. Dante falls here from Endless Infernum and has to fight all the demons in order to unlock teleport leading back to Endless Infernum.

Second Floor

 * Chamber of Echoes (second floor) - the upper portion of the room, which consists of three spiral roundwalks, which form three mini-floors, just like on the first floor. Passage between this one and the first one is blocked by walls. There are exits to Incandescent Space via green door and Endless Infernum via yellow one. There is a big clock-like mechanism on the wall with glowing hyerogliphs behind it. In the highest point of the chamber, beside the mechanism, is a pedestal for the Astronomical Board. If it is placed there, the wall, preventing passage between floors will be removed and Jump Pad is activated downstairs.
 * Incandescent Space (a.k.a. Astral Chamber) - a room with some gear-like looking mechanisms, where Hell Gluttonies are first met by Dante. It can be accessed from Chamber of Echoes or Silence Statuary (via elevator). A small area of this room, that hosts the Astronomical Board and where Dante first meets Jester, is separated by iron bars and can only be accessed through Giantwalker Chamber. The name of this area is changed to Astral Chamber from Mission 6 for unknown reasons.
 * Endless Infernum - a room that connects Chamber of Echoes, Giantwalker Chamber and Surge of Fortunas. The later is on separated by a pit with a catwalk above it, that is just above the Chamber of Sins. The catwalk collapses when Dante tries to cross it, but he manages to cross the pit using the Soul of Steel, which he then placed in the wall to open the doors to the Surge of Fortunas.
 * Giantwalker Chamber - a long wide corridor, that is entered through Endless Infernum and leads to the separated portion of Incandenscent Space. A Gigaped, which travels using the tunnels in the walls, is first met and killed by Dante here. Later Jester introduces Blood-goyles to Dante in this place and creates a first portal to his dimension (Special Edition only).
 * Surge of Fortunas - a room with staircase leading to the elevator, that goes to the Azure Garden in the Central Temen-ni-gru. There is a mechanism, that activates the elevator in the room. While Dante rides the elevator, Hell Prides appear, and he has to fight them quickly before more arrive, and overload the elevator, making it return down, This room can only be entered from Endless Infefnum, because the elevator provides one-way trip. A secret mission "Untouchable" can be accessed here through a pattern that glows with red.
 * Heavenrise Chamber (lower) - a lower part of the big vertical room with many Jump Pads, that allow to rise to the top. In the bottom of it is an entrance to The Divine Library.
 * The Divine Library - a large library, that can only be accessed trough Heavenrise Chamber. It contains many Damned Pawns, of witch come to life when attacked, apart from two different-colored ones, that will remain dormant. When Dante first enters the library, the exit is shut by a blue seal, which disappears when he picks up the Orihalcon fragment, which is located underneath one of the pawns.

Forbidden Land
The Forbidden Land is the lowest portions of Temen-ni-gru, and its entrance,, is just below ground level. However, the only intentional entrance to Forbidden Land available to Dante is an inactive elevator, so he instead reaches the area by crashing Leviathan through its roof. The Forbidden Land is divided into four sections guarded by the final gatekeepers. The first floor is guarded at both ends by Nevan and Beowulf the Lightbeast, and is separated into the two sections by means of two swiveling bridges powered by the Neo Generator.

Nevan's lair, the, resembles a stage built into a limestone cavern, and features a stage complete with speakers, stage lights, spotlights, and pyrotechnic effects. It is sealed by a door engraved with the image of a nude woman, which must be unlocked by placing the Ambrosia in the carving's hands. Just outside of the room is a pedestal which holds the Stone Mask that Dante needs to get to the first Neo Generator.

After slaying both gatekeepers and reactivating both bridges, Dante opens the path to the and the, guarded by Geryon the Timesteed. After that is the deepest heart of the tower, the where the seal on the Temen-ni-gru can be broken.

Background
The Temen-ni-gru's name is drawn from the Neo-Sumerian, named "E-temen-nigur(u)", literally "house whose foundation creates terror" in Sumerian. It was a structure built to serve as both an administrative center of the city, and as a shrine to Ur's patron deity, the moon god Nanna, or ; Temen-ni-gru's use to worship Sin as immorality is a pun on this.

The Temen-ni-gru's design draws heavily from the, especially the painting of it made by Pieter Bruegel the Elder. While the Tower of Babel was built to invade Heaven, the Temen-ni-gru was built as a gateway to Hell.

The seven demonic bell statues left throughout the tower are a reference to the : Pride, Greed, Lust, Envy, Gluttony, Wrath, and Sloth. These seven concepts also appear in the Divine Comedy as layers of Purgatory, the mountain which Dante climbs to heaven, just as the bells are each found at different floors of the tower.

The seven demonic gatekeepers (e.g, Cerberus, Beowulf, etc.) also represent the 7 deadly sins. This goes for:

Cerberus - Gluttony

Agni and Rudra - Sloth

Beowulf - Wrath

Nevan - Lust

Doppelganger - Pride

Geryon - Greed

Leviathan - Envy